Method for manufacturing mill roll, mill roll and manufacturing apparatus of mill roll

ABSTRACT

A method for manufacturing a mill roll including a preheating process for joining end portions  16  to  19  of a roll barrel member  13  and/or shaft materials  14, 15 , and a friction pressure welding process strongly pressing and joining the shaft materials  14, 15  to a core material  11  after frictionally heating the joining end portions  16  to  19  by rotating the shaft materials  14, 15  while pressing to the core material  11 , and a manufacturing apparatus including first and second holding means  29, 23  for the roll barrel member  13  and the shaft materials  14, 15 , a rotating means rotating the shaft materials  14, 15 , a pressing means  24  pressing the core material  11  and the shaft materials  14, 15  in an axial direction, and a preheating means  31  preheating the joining end portions  16  to  19  of the roll barrel member  13  and the shaft materials  14, 15.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a mill roll,a mill roll and a manufacturing apparatus of a mill roll for use in arolling equipment for iron manufacture.

BACKGROUND ART

Conventionally, for example, in rolling of shaped steel, in order toupgrade the quality of rolled materials and to achieve labor-savings andenergy-savings, mill rolls that can tolerate comparatively severerolling conditions and have long lives have been in demand.

Due to this, for instance, as described in Patent Literature 1, millrolls such as one in which a surface part of a roll barrel member iscomposed of hard metal (e.g., high-speed steel type multi-alloyed whitecast iron) have been being used. This mill roll has been manufactured byremoving a mill roll, in which a roll barrel member and shaft materialsare integrated, from a material for rolls by scraping, the material forrolls being provided with a hard metal layer formed on an outercircumference of a core material, the shaft materials being singlyprovided on both sides in an axial direction of the roll barrel member.

However, when removing a mill roll having long shaft materials from amaterial for rolls by scraping, the amount of extra machining allowanceat the time of removing by scraping increases, failing to shorten themanufacturing time. Also, running costs of cutting blades are incurred,which is uneconomical. Moreover, since it becomes impossible tomanufacture a plurality of mill rolls from one material for rolls, forexample, there is a need to prepare a new material for rolls, and it hasbeen difficult to shorten the delivery time of and to reduce themanufacturing cost of mill rolls.

Therefore, for example, as with Patent Literature 2, there has been aproposal of a method for joining a roll barrel member and shaftmaterials by providing grooves singly to and arranging shaft materialssingly on both sides of the roll barrel member and welding therespective grooves.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2000-158020

Patent Literature 2: Japanese Unexamined Patent Application PublicationNo. 2005-324204

SUMMARY OF INVENTION Technical Problem

However, since mill rolls are used in rolling equipments for ironmanufacture on which major loads are applied, when joining a roll barrelmember and shaft materials, it is easy for the interfaces to be damaged,and it has been difficult to achieve a further extension of lives ofmill rolls.

Additionally, in a technique described in Patent Literature 2, shaftmaterials are prone to being welded eccentrically or crookedly withrespect to a roll barrel member, which makes post-welding stress reliefnecessary. Since it is difficult to perform the stress reliefcompletely, there has been a need to use shaft materials that aresomewhat thick.

The present invention has been made in view of the above circumstances,and an object thereof is to provide a method for manufacturing a millroll, a mill roll, and a manufacturing apparatus of a mill roll in whicha mill roll can be manufactured in a shortened work period and at a lowcost and an ever-longer life of a mill roll can be achieved.

Solution to Problem

In order to achieve the above object, according to a first aspect of thepresent invention, there is provided a method for manufacturing a millroll, including: a roll barrel member having a hard tinkering hardfacinglayer formed on an outer circumference of a columnar core materialconsisting of chromium-molybdenum steel or carbon steel; and shaftmaterials consisting of chromium-molybdenum steel and being singlyprovided on both sides in an axial direction of the core material,

wherein

-   diameters of joining end portions of the shaft materials are made    smaller than a diameter of the core material, the method further    including:-   a preheating process for preheating either one or both of at least    joining end portions of the roll barrel member and the joining end    portions of the shaft materials to a pre-set temperature; and-   a friction pressure welding process for, with axial centers of the    shaft materials aligned with an axial center of the core material,    joining the core material and the shaft materials by strongly    pressing the shaft materials to the core material after frictionally    heating the joining end portions of the core material and the shaft    materials by rotating the shaft materials while pressing the shaft    materials to the core material.

In the method for manufacturing a mill roll according to the firstaspect of the present invention, the diameters of the joining endportions of the shaft materials can be 0.86-fold or more and 0.96-foldor less of the diameter of the core material.

In the method for manufacturing a mill roll according to the firstaspect of the present invention, it is preferred that the core materialprojects from end portions of the roll barrel member. A projectionamount of 1 to 10 mm is enough in this case, however, the presentinvention is not limited to these numerical values.

In the method for manufacturing a mill roll according to the firstaspect of the present invention, it is preferred that, after thefriction pressure welding process, a metal surface is exposed bymachining interfaces of the roll barrel member and the shaft materials,and circumferential welding is performed on the interfaces.

In the method for manufacturing a mill roll according to the firstaspect of the present invention, it is preferred that a preheattemperature for the joining end portions in the preheating process is500° C. or higher and a melting point of the shaft materials or lower.

In the method for manufacturing a mill roll according to the firstaspect of the present invention, a used roll having the new tinkeringhardfacing layer formed on the outer circumference of the roll barrelmember can be used as the roll barrel member.

In the method for manufacturing a mill roll according to the firstaspect of the present invention, it is preferred that the tinkeringhardfacing layer on the outer circumference is partially or entirelyremoved from the used roll by machining after annealing.

In the method for manufacturing a mill roll according to the firstaspect of the present invention, shaft materials cut off and separatedfrom a used roll can be used as the shaft materials.

In order to achieve the above object, a mill roll according to a secondaspect of the present invention is manufactured by the method formanufacturing a mill roll according to the first aspect of the presentinvention.

In order to achieve the above object, according to a third aspect of thepresent invention, there is provided a manufacturing apparatus of a millroll used for the method for manufacturing a mill roll according to thefirst aspect of the present invention, including:

-   a first holding means for holding the roll barrel member    horizontally or perpendicularly;-   a second holding means for holding the shaft materials, the shaft    materials being aligned with the axial center of the roll barrel    member;-   a rotating means provided to the second holding means for rotating    the shaft materials centering on the axial centers of the shaft    materials;-   a pressing means provided to either the first holding means or the    second holding means for pressing the core material and the shaft    materials in the axial direction while joint surfaces of the core    material and the shaft materials are facing one another; and-   a preheating means for preheating the joining end portions of both    the roll barrel member and the shaft materials.

In the manufacturing apparatus of a mill roll according to the thirdaspect of the present invention, it is preferred that the preheatingmeans is composed of a plurality of burners each arranged facing therespective joining end portions of the roll barrel member and the shaftmaterials that are arranged opposed to one another with a space inbetween.

In the manufacturing apparatus of a mill roll according to the thirdaspect of the present invention, it is preferred that the plurality ofburners arranged facing the joining end portions are arranged moredensely in the central portions of the joining end portions than in theperipheral portions of the joining end portions.

In the manufacturing apparatus of a mill roll according to the thirdaspect of the present invention, it is preferred that a heat-resistantmember is provided on the side of flame jetting ports of the pluralityof burners.

In the manufacturing apparatus of a mill roll according to the thirdaspect of the present invention, it is preferred that the plurality ofburners are provided with a water-cooling means.

In the manufacturing apparatus of a mill roll according to the thirdaspect of the present invention, the preheating means can alternativelybe provided to a moving means movable between a preheating position anda non-preheating position, the preheating position preheating thejoining end portions of the roll barrel member and the shaft materials,the non-preheating position being located lateral to the preheatingposition.

In the manufacturing apparatus of a mill roll according to the thirdaspect of the present invention, it is preferred that the preheatingmeans has a burner and a robot arm, and determines a direction and amovement locus of the burner based on the robot arm, the burnersimultaneously or serially heating the joining end portions of the rollbarrel member and the shaft materials, the robot arm having the burnerattached at the tip portion thereof.

In the manufacturing apparatus of a mill roll according to the thirdaspect of the present invention, it is preferred that the burnerconsists of a first burner and a second burner, the first burnerpreheating the joining end portions of the roll barrel member, thesecond burner preheating the joining end portions of the shaftmaterials.

Advantageous Effects of Invention

In the method for manufacturing a mill roll, the mill roll and themanufacturing apparatus of a mill roll according to the presentinvention, since the roll barrel member and the shaft materials arejoined by the preheating process and the friction pressure weldingprocess, a mill roll can be manufactured in a shortened work period andat a low cost, and an ever-longer life of a mill roll can be achieved.

Additionally, since the diameters of the joining end portions of theshaft materials are made smaller than the diameter of the core material,the core material and the shaft materials can be welded (frictionpressure welding) in direct contact with one another with the axialcenters surely aligned with one another, the core material consisting ofchromium-molybdenum steel or carbon steel, the shaft materialsconsisting of chromium-molybdenum steel. Since the hard tinkeringhardfacing layer on the outer side of the roll barrel member does notcome into contact with the shaft materials, friction pressure weldingthat has enough joint strength for a mill roll and gives few buckles anddeformations can surely be performed.

Especially, when the core material is projecting from the roll barrelmember, the shaft materials do not come into contact with the hardtinkering hardfacing layer of the roll barrel member even more, andfriction pressure welding can surely be performed.

Moreover, in the case of the manufacturing apparatus of a mil rollaccording to the present invention, when using the burner provided atthe tip portion of the robot arm as the preheating means for preheatingthe joining end portions of the roll barrel member and the shaftmaterials, by controlling the robot arm, arbitrary spots of the rollbarrel member and the shaft materials can be heated by the burner atarbitrary timing. Also, by changing a program of the robot arm, regionsto be heated can be changed in conformity with a roll barrel member andshaft materials having arbitrary diameters.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram of a mill roll according to oneembodiment of the present invention.

FIG. 2 is an explanatory diagram of a method for manufacturing a millroll according to a first embodiment of the present invention.

FIGS. 3(A) and 3(B) are a side sectional view and a front view,respectively, of a preheating means of a manufacturing apparatus of amill roll used for the method for manufacturing a mill roll.

FIG. 4 is a front view of a driving means provided with the preheatingmeans.

FIG. 5 is an explanatory diagram of a method for manufacturing a millroll according to a second embodiment of the present invention.

FIGS. 6(A) to 6(C) are explanatory diagrams of a preheating means usedfor the present invention.

FIG. 7 is an explanatory diagram of a different preheating means usedfor the present invention.

DESCRIPTION OF EMBODIMENTS

Next, with reference to the accompanying drawings, descriptions will begiven on embodiments of the present invention for a better understandingof the present invention.

First, with reference to FIG. 1, descriptions will be given on a millroll 10 according to one embodiment of the present invention.

The mill roll 10 is used in the rolling of iron and steel, especially inhot rolling work and cold rolling work (rolling and straightening) ofthin plates, steel bars, wire rods or shaped steel. The mill roll 10 isa roll having received a predetermined processing treatment inaccordance with the intended purpose.

The mill roll 10 is provided with a roll barrel member 13 and shaftmaterials 14, 15, the roll barrel member 13 having a tinkeringhardfacing layer 12 on an outer circumference of a columnar corematerial 11, the shaft materials 14, 15 each being provided on bothsides in an axial direction of the core material 11.

Regarding the dimension of the mill roll 10, the outer diameter (barreldiameter) D of the roll barrel member 13 is, for example, about 300 to900 mm, the width (barrel length) W is, for example, about 1500 to 2500mm, and the total length L including the shaft materials 14, 15 is, forexample, about 4000 to 7000 mm.

Here, the core material 11 of the roll barrel member 13 consists ofchromium-molybdenum (Cr—Mo) steel or carbon steel, and the shaftmaterials 14, 15 consist of chromium-molybdenum (Cr—Mo) steel.

The tinkering hardfacing layer 12 formed on the outer circumference ofthe core material 11 consists of, for example, hard materials such asferrous outer layer material (with hardness of shore (HS) of about 70 to100) described in Japanese Unexamined Patent Application Publication No.2012-110968 and high-speed steel type multi-alloyed white cast iron (anexample of high-speed steels). The thickness of the tinkering hardfacinglayer 12 can be changed variously depending on the intended purposes,however, the thickness thereof is, for example, about 50 to 150 mm.

Since the roll barrel member 13 can be manufactured by, for example, amethod disclosed in Japanese Unexamined Patent Application PublicationNo. 2000-158020, descriptions will be omitted here.

The above mill roll 10 is made by separately forming the roll barrelmember 13 and the shaft materials 14, 15, frictionally joining a joiningend portion 16 and a joining end portion 17, and frictionally joining ajoining end portion 18 and a joining end portion 19, the joining endportion 16 being provided on one side of the core material 11 of theroll barrel member 13, the joining end portion 17 being provided to theshaft material 14 on one side, the joining end portion 18 being providedon the other side of the core material 11, the joining end portion 19being provided to the shaft material 15 on the other side.

However, as needed, it is possible to form only a shaft material on oneside of a core material integrally with the core material by machining,to form only a shaft material on the other side of the core materialseparately from the core material, and to frictionally join joining endportions of the core material and the shaft material.

Since the shaft materials 14, 15 are frictionally joined to the rollbarrel member 13 as just described, in order for the core material 11and the shaft materials 14, 15 to be joined in good condition, thediameters (outer diameters) of the joining end portions 17, 19 of theshaft materials 14, 15 are made smaller than the diameter of the corematerial 11. More specifically, it is preferred that the diameters ofthe joining end portions 17, 19 of the shaft materials 14, 15 are0.86-fold or more and 0.96-fold or less of the diameter of the corematerial 11.

Also, it is preferred that circumferential welding (build-up welding) isperformed on the interfaces (boundary portions in a circumferentialdirection) of the roll barrel member 13 and the shaft materials 14, 15for the reinforcement. For example, MIG welding method or TIG weldingmethod in which a filler metal such as high tensile strength steel(hi-ten) is used can be applied to this welding.

Here, as the roll barrel member 13, an unused roll barrel member (unuseditem) can be used; however, a roll barrel member of a used roll (useditem) can also be used. When using a used item, after cutting off andremoving shaft materials on both sides (or one side) in an axialdirection of the used roll, on the outer circumference of the obtainedroll barrel member, machining is performed if necessary, and then a newtinkering hardfacing layer having the above-described structure becomesformed.

Additionally, in the same way, unused shaft materials (unused items) canbe used as the shaft materials 14, 15, however, shaft materials of aused roll (used items) can also be used. When using used items, shaftmaterials cut off and separated from a used roll are machined (diameterreduction) as needed.

Next, with reference to FIGS. 1 to 4, descriptions will be given on amanufacturing apparatus of a mill roll (hereinafter also simply referredto as a manufacturing apparatus) 20 according to a first embodiment ofthe present invention. The manufacturing apparatus of a mill roll 20includes a base stand 21, a plurality (here, the number is three) ofclamps 22, a chuck (an example of second holding means) 23 and ahydraulic cylinder (an example of pressing means) 24, the plurality ofclamps 22 being provided on the base stand 21 and holding the rollbarrel member 13, the chuck 23 holding the shaft material 14 (or theshaft material 15, the same applies hereafter), the hydraulic cylinder24 pressing the roll barrel member 13 held by the plurality of clamps 22in an axial direction thereof.

A first supporting stand 25 provided with the hydraulic cylinder 24 isattached and fixed on the end of one side in a longitudinal direction ofthe base stand 21 (the side of the roll barrel member 13). A secondsupporting stand 26 provided with the chuck 23 is attached and fixed onthe end of the other side in a longitudinal direction of the base stand21 (the side of the shaft material 14).

The chuck 23 holds the base side of the shaft material 14 in a way thatkeeps the shaft material 14 in a horizontal state. The chuck 23 isprovided with a speed reducer and a motor (not illustrated) which areexamples of rotating means for rotating the shaft material 14 centeringon the axial center of the shaft material 14. A steady rest means 27 isarranged at a position anterior to the chuck 23 (tip side of the shaftmaterial 14), the steady rest means 27 controlling and furtherpreventing the run-out of the axial center position of the shaftmaterial 14 held by the chuck 23 when the shaft material 14 rotates.

Between the supporting stand 25 and the supporting stand 26 eacharranged on the ends of both sides in a longitudinal direction of thebase stand 21, there is a table 28 movable along the longitudinaldirection of the base stand 21. On top of the table 28, the plurality ofclamps 22 are attached and fixed in the longitudinal direction of thebase stand 21 at intervals.

This enables the roll barrel member 13 and the shaft material 14 to bearranged horizontally on the base stand 21 with the axial centers of theroll barrel member 13 and the shaft material 14 aligned with each other.

Here, a first holding means 29 has the clamps 22 and the table 28. Also,the hydraulic cylinder 24 is in contact with the end of one side in alongitudinal direction of the table 28, which means that the hydrauliccylinder 24 is provided to the first holding means 29.

The roll barrel member 13 can thereby be pressed to the shaft material14 through the first holding means 29 by using the hydraulic cylinder24. Due to the pressing force, there is a possibility that a spacebetween the upper parts of the supporting stand 25 and the supportingstand 26 becomes wider at this point, however, this can be preventedsince the lower parts of the supporting stand 25 and the supportingstand 26 are connected by the base stand 21, and the upper parts areconnected by a connecting rod 30.

As described above, the descriptions have been given on a case in whichthe roll barrel member 13 is pressed to the side of the shaft material14 by the hydraulic cylinder 24 provided to the first holding means 29here. However, considering the weight, length and the like of the rollbarrel member 13, it is preferred that the shaft material 14 is pressedto the side of the roll barrel member 13 by fixing the arrangingposition of the roll barrel member 13 (without moving the position ofthe roll barrel member 13), attaching a chuck (and additionally, asteady rest means) to a table movable in the longitudinal direction ofthe base stand 21, and providing a hydraulic cylinder (an example ofpressing means) to the chuck.

The pressing means is not limited to a hydraulic cylinder, and can beother things capable of pressing the core material 11 and the shaftmaterial 14 in an axial direction such as a pneumatic cylinder and anelectric cylinder.

As illustrated in FIGS. 2, 3(A), 3(B) and 4, there is a preheating means31 provided in between the chuck 23 and the clamps 22.

The preheating means 31 is composed of a plurality of burners 32arranged facing the respective joining end portions 16 and 17 of theroll barrel member 13 and the shaft material 14 (same applies to theshaft material 15), the roll barrel member 13 and the shaft material 14being held by the clamps 22 and the chuck 23, respectively, and beingarranged opposed to each other with a space in between. The preheatingmeans 31 preheats both the joining end portion 16 of the roll barrelmember 13 and the joining end portion 17 of the shaft material 14 to apre-set temperature.

As illustrated in FIGS. 3(A) and 3(B), the preheating means 31 isprovided with a water-cooling means 33.

The water-cooling means 33 has a disk-shaped water-cooling jacket 34 anda disk-shaped water-cooling jacket 35, the water-cooling jacket 34 beingarranged opposed to the joint surface of the core material 11 of theroll barrel member 13 with a space in between, the water-cooling jacket35 being arranged opposed to the joint surface of the shaft material 14with a space in between. These water-cooling jackets 34, 35 are singlyattached and fixed to both sides in a thickness direction of a mountingstand 36 with axial centers of the water-cooling jackets 34, 35 alignedwith each other, and the plurality of burners 32 are attached and fixedto each of these water-cooling jackets 34, 35. Pipe arrangements 37, 38are connected to the upper and lower portions of the water-coolingjackets 34, 35, the pipe arrangements 37, 38 delivering water to anddraining water from the water-cooling jackets 34, 35.

Also, ceramic (e.g., alumina) heat-resistant plates (an example ofheat-resistant members) 39, 40 are individually provided on the obversesurface sides of each of the water-cooling jackets 34, 35, i.e., theside of the flame jetting ports of the plurality of burners 32 (the sideof the surface opposed to the joint surface of the roll barrel member 13and the side of the surface opposed to the joint surface of the shaftmaterial 14). Additionally, opening portions 41 are formed in theheat-resistant plates 39, 40 in conformity with the positions of theflame jetting ports of each of the burners 32.

On the other hand, there are gas supply chambers 43, 44 individuallyprovided on the reverse surface sides of each of the water-coolingjackets 34, 35, the gas supply chambers 43, 44 supplying gas deliveredfrom a gas supply tube 42 to each of the burners 32.

By providing the water-cooling means 33 and the heat-resistant plates39, 40 to the plurality of burners 32 as just described, it becomespossible to control and even prevent the case in which the fittingportions of the burners 32 become deformed or even melted as a result ofreaching a high temperature due to the flame of the burners 32 recoilingon each joint surface in the middle of preheating both the joining endportion 16 of the roll barrel member 13 and the joining end portion 17of the shaft material 14 by the plurality of burners 32.

Here, the descriptions have been given on the case in which theplurality of burners 32 are provided with both the water-cooling means33 and the heat-resistant plates 39, 40, however, depending on the usagecondition of the burners 32 (such as a preheat temperature), it ispossible to use neither, or to use only either one of the water-coolingmeans 33 and the heat-resistant plates 39, 40.

As illustrated in FIGS. 3(B) and 4, the plurality of burners 32 arearranged at the axial center position of the water-cooling jacket 34(the same applies to the water-cooling jacket 35) and concentricallyarranged centering on the axial center position of the water-coolingjacket 34. Especially, in this embodiment, since the shaft material 14(the same applies to the shaft material 15) is frictionally joined tothe roll barrel member 13, in order for the core material 11 and theshaft material 14 to be joined in good condition, the plurality ofburners 32 arranged facing the respective joining end portions 16, 17are arranged more densely in the central portions (axial centerportions) of the joining end portions 16, 17 (water-cooling jackets 34and 35) than the peripheral portions thereof.

The temperature can thereby be made higher in the central portions ofthe respective joining end portions 16, 17 than in the peripheralportions thereof.

Here, the descriptions have been given on the case in which theplurality of burners 32 are used as the preheating means 31, however,the preheating means 31 is not limited to a plurality of burners, andfor example, an electromagnetic induction heating coil and the like canbe used as well.

As illustrated in FIG. 4, the preheating means 31 is provided to amoving means 47 that enables moves between a preheating position 45 (theposition illustrated by chain double-dashed lines in the preheatingmeans 31 in FIG. 4) and a non-preheating position 46 (the positionillustrated by solid lines in the preheating means 31 in FIG. 4, i.e., astandby position), the preheating position 45 preheating the joining endportions 16, 17 of the roll barrel member 13 and the shaft material 14(the same applies to the shaft material 15), the non-preheating position46 being located lateral to the preheating position 45.

The moving means 47 has a guide rail 48 and a carrying stand 49, theguide rail 48 being arranged extending between the preheating position45 and the non-preheating position 46, the carrying stand 49 beingtravelable on the guide rail 48 and having the lower end portion of themounting stand 36 of the preheating means 31 attached and fixed thereto.

The preheating means 31 can thereby be made to reciprocate between thepreheating position 45 and the non-preheating position 46.

The moving means 47 is provided with a gas supply hose 50 that suppliesgas to the burners 32 of the preheating means 31.

The tip end portion of the gas supply hose 50 is connected to thecarrying stand 49 and structured to be capable of supplying gas to thegas supply tube 42 connected to the carrying stand 49. On the otherhand, the base end portion of the gas supply hose 50 is connected to acarriage 51 made travelable on the side of the base stand 21 and inparallel with the base stand 21.

When the preheating means 31 reciprocates between the preheatingposition 45 and the non-preheating position 46, the gas supply hose 50is supported and guided by a guide roller 52 (looper mechanism), whichprevents the gas supply hose 50 from touching a floor surface 53.

The manufacturing apparatus of a mill roll 20 is also provided with athermometer, a torque detector, a pressure gauge and the like, thethermometer measuring temperatures of the preheated roll barrel member13 and the preheated shaft material 14, the torque detector detectingtorque at the time of pressing the core material 11 and the shaftmaterial 14, the pressure gauge measuring a pressure applied at the timeof pressing.

Respective functions of the above motor, the above hydraulic cylinder 24and the above preheating means 31 can be controlled by a controlapparatus (not illustrated). The control apparatus also supervises eachvalue measured by the thermometer, the torque detector and the pressuregauge, and is capable of controlling respective performances of themotor, the hydraulic cylinder 24 and the preheating means 31 based onthese measured values.

Therefore, after making the joint surfaces of the core material 11 andthe shaft materials 14, 15 face to face with one another under acondition where the axial centers of the preheated shaft materials 14,15 are aligned with the axial center of the preheated core material 11,rotating the chuck 23 (the shaft materials 14, 15) by the motor whilepressing the core material 11 to the shaft materials 14, 15 by thehydraulic cylinder 24, and frictionally heating the joining end portions16 to 19 of the core material 11 and the shaft materials 14, 15, thecore material 11 can be strongly pressed and joined to the shaftmaterials 14, 15 by the hydraulic cylinder 24. Additionally, strongpressing can also be performed by that which is other than the hydrauliccylinder 24.

Next, with reference to FIGS. 1 and 5, descriptions will be given on amanufacturing apparatus of a mill roll (hereinafter also simply referredto as a manufacturing apparatus) 60 according to a second embodiment ofthe present invention.

The manufacturing apparatus of a mill roll 60 includes a base stand 61,a clamp (an example of first holding means) 62 and a chuck (an exampleof second holding means) 63, the clamp 62 being provided on the basestand 61 and holding the roll barrel member 13, the chuck 63 holding theshaft material 14 (or the shaft material 15, the same applieshereafter).

The clamp 62 holds the roll barrel member 13 with the axial center ofthe core material 11 in a perpendicular direction. The chuck 63 isarranged above the clamp 62 so that the axial center of the shaftmaterial 14 held by the chuck 63 becomes aligned with the axial centerof the core material 11 (i.e., so that the axial center of the shaftmaterial 14 lies in a perpendicular direction).

The above chuck 63 is provided with a motor (not illustrated) that is anexample of rotating means for rotating the shaft material 14 held by thechuck 63 centering on the axial center of the shaft material 14.

The chuck 63 is further provided with an unillustrated pressing means(e.g., a hydraulic cylinder and the like), the pressing means making theshaft material 14 held by the chuck 63 perform vertical motions withrespect to the roll barrel member 13 held by the clamp 62 and pressingthe core material 11 and the shaft materials 14, 15 in the axialdirection with the joint surfaces of the core material 11 and the shaftmaterials 14, 15 facing one another. A pressing means can alternativelybe provided to the side of a clamp.

There is a preheating means (not illustrated) provided between the chuck63 and the clamp 62. That which has a similar function as that of theearlier-described preheating means 31 can be used as the preheatingmeans.

As with the manufacturing apparatus of a mill roll 20 described earlier,the manufacturing apparatus of a mill roll 60 is provided with athermometer, a torque detector, and even a pressure gauge and the like.

Respective performances of the above motor, the above pressing means andthe above preheating means can be controlled by a control apparatus (notillustrated). The control apparatus also supervises each value measuredby the thermometer, the torque detector and the pressure gauge, and iscapable of controlling respective performances of the motor, thepressing means and the preheating means based on these measured values.

Therefore, after making the joint surfaces of the core material 11 andthe shaft materials 14, 15 face to face with one another under acondition where the axial centers of the shaft materials 14, 15 arealigned with the axial center of the preheated core material 11,rotating the chuck 63 (the shaft materials 14, 15) by the motor whilepressing the shaft materials 14, 15 to the core material 11 by thepressing means, and frictionally heating the joining end portions 16 to19 of the core material 11 and the shaft materials 14, 15, the shaftmaterials 14, 15 can be strongly pressed and joined to the core material11 by the pressing means.

Next, with reference to FIGS. 1 to 4, descriptions will be given on amethod for manufacturing a mill roll according to the first embodimentof the present invention.

Methods for manufacturing a mill roll include a preparatory process, apreheating process, a friction pressure welding process and a finishingprocess.

First, descriptions will be given on the preparatory process.

In the preparatory process, the roll barrel member 13 and the shaftmaterials 14, 15 are prepared.

When using an unused roll barrel member (unused item) as the roll barrelmember 13, a long core material having the same diameter as that of thecore material 11 (a core material having a length equal to a pluralityof core materials 11) is firstly manufactured by machining a longmaterial for rolls (Cr—Mo steel or carbon steel). Next, after formingthe tinkering hardfacing layer 12 on the outer circumference of themanufactured long core material, the roll barrel member 13 is obtainedby cutting off this long core material.

A shaft material on only one side of a core material may be formedintegrally with the core material by machining from a material forrolls.

When using a roll barrel member of a used roll (used item) as the rollbarrel member 13, after cutting off and removing shaft materials on bothsides in an axial direction of the used roll, a new tinkering hardfacinglayer 12 is formed on the outer circumference of the obtained rollbarrel member. It is preferred that the new tinkering hardfacing layer12 is formed by removing part of or the entire existing tinkeringhardfacing layer on the outer circumference (with the remainingthickness of 0 mm or more than 0 mm and about 30 mm or less) bymachining after annealing a roll barrel member in which shaft materialson both sides in an axial direction of a used roll are cut off andremoved.

Additionally, a shaft material on only one side of a mill roll could becut off from a used roll.

Here, it is preferred that projecting portions (projection amount in theaxial center direction: e.g., about 1 to 100 mm, more preferably, 2 to10 mm) having diameters equal to or larger than the diameters of theshaft materials 14, 15 are preliminarily formed in the joining endportions 16 and 18 of the above roll barrel member 13 (the core material11) to be joined to the shaft materials 14, 15.

When using an unused shaft material (unused item) as the shaft material14 (the same applies to the shaft material 15), the shaft material 14 inwhich the end face of the joining end portion 17 is flat is obtained bymachining/cutting off (machining and cutting off) a material for rolls(Cr—Mo steel).

When using a shaft material of a used roll (used item), a shaft materialcut off and separated from a used roll is machined (diameter reduction)as needed. In this case, as with the above roll barrel member of theused roll, it is preferred to preliminarily anneal before machining.

Here, the diameter of the joining end portion 17 of the shaft material14 is made smaller than that of the core material 11 (0.86- to 0.96-foldof the diameter of the core material 11).

The roll barrel member 13 and the shaft materials 14, 15 obtained by theabove method are carried to the manufacturing apparatus of a mill roll20, the clamps 22 are made to hold the roll barrel member 13 and thechuck 23 is made to hold the shaft material 14 (the same applies to theshaft material 15).

Here, the relative position of the clamps 22 and the chuck 23 is alsoadjusted in order to make the axial center of the core material 11 ofthe roll barrel member 13 and the axial center of the shaft material 14aligned with each other.

Next, descriptions will be given on the preheating process.

In the preheating process, the joining end portion 16 of the roll barrelmember 13 and the joining end portion 17 of the shaft material 14 (orthe shaft material 15, the same applies hereafter) are preheated to apre-set temperature by the earlier-described preheating means 31.

First, the carrying stand 49 of the moving means 47 is moved, and thepreheating means 31 located at the non-preheating position 46 is movedto the preheating position 45 (position where the preheating means 31becomes arranged facing the respective joining end portions 16, 17 ofthe roll barrel member 13 and the shaft material 14).

Next, the joining end portions 16, 17 are preheated to theabove-described temperature.

Since the earlier-described preheating means 31 is used in thepreheating, the temperatures rise higher in the central portions of therespective joining end portions 16, 17 of the core material 11 and theshaft material 14 than in the peripheral portions thereof (e.g., thetemperatures are made higher in the central portions than in theperipheral portions within the range of 50 C.° or higher and 150 C.° orlower). Projection amount in an axial center direction in the centralportions of the respective joining end portions 16, 17 of the corematerial 11 and the shaft material 14 thereby becomes larger than in theperipheral portions of the respective joining end portions 16, 17.

Since it is only necessary to preheat at least the joining end portion16 of the roll barrel member 13 and the joining end portion 17 of theshaft material 14, preheating can be performed on part of the rollbarrel member 13 that includes the joining end portion 16 or the entireroll barrel member 13, and part of the shaft material 14 that includesthe joining end portion 17 or the entire shaft material 14.

Also, preheating can be performed only on the joining end portion 16 ofthe roll barrel member 13 or only on the joining end portion 17 of theshaft material 14 as needed. Additionally, an end face of at least oneof the respective joining end portions 16, 17 of the core material 11and the shaft material 14 can be preliminarily machined in the shape ofa roughly circular arc, a chevron, a convex and the like in which theprojection amount in the axial center direction in the central portionwith respect to other parts (parts excluding the central portion) islarger by 0.1 mm to a few mm. In this case, a heating means capable ofnearly evenly heating the joining end portion can be used.

Here, although a preheat temperature (the temperatures in the centralportions of the respective joining end portions 16, 17 of the corematerial 11 and the shaft material 14) is not specifically limited aslong as the roll barrel member 13 and the shaft material 14 becomejoined in good condition by the temperature, it is especially good topreheat at a temperature of 500 C.° or higher and a melting point of theshaft material 14 or lower.

When the preheat temperature is lower than 500 C.°, there is apossibility that the joint strength between a roll barrel member and ashaft material cannot be heightened enough since the temperature is toolow. On the other hand, when the preheat temperature exceeds a meltingpoint of a shaft material, there is a possibility that, for example, theshaft material becomes softened and the metallic structure changes,making the shaft material unusable as a shaft material.

Therefore, the preheat temperature is set at 500 C.° or higher and themelting point of the shaft material 14 or lower. However, it ispreferred that the lower limit is 550 C.°, or even 600 C.°, and it ispreferred that the upper limit is “the melting point of the shaftmaterial 14 −50 C.°,” or even “the melting point of the shaft material14 −100 C.°.”

After preheating is finished in this manner, the preheating means 31located at the preheating position 45 is moved to the non-preheatingposition 46 by moving the carrying stand 49 of the moving means 47.

Next, descriptions will be given on the friction pressure weldingprocess.

In the friction pressure welding process, the shaft material 14 isjoined to the roll barrel member 13.

First, under a condition where the axial center of the shaft material 14is aligned with the axial center of the core material 11 preheated inthe above preheating process, by pressing the core material 11 to theshaft material 14 through the hydraulic cylinder 24 while rotating thechuck 23 (the shaft materials 14, 15) through the motor, the joining endportions 16, 17 of the core material 11 and the shaft material 14 becomefrictionally heated.

Here, the pressing force of the core material 11 and the rotating speedof the shaft material 14 are not specifically limited as long asfrictional heating can be adequately performed. The pressing force is,for example, about 10 MPa or more and 40 MPa or less (preferably, thelower limit is 15 MPa and the upper limit is 30 MPa). The rotating speedis, for example, about 100 rpm (rounds/minute) or more and 500 rpm orless (preferably, the lower limit is 150 rpm and the upper limit is 300rpm).

The core material 11 and the shaft material 14 thereby come into contactwith each other beginning with the central portions thereof and becomefrictionally heated/melted (frictionally heated, and then melted), andthe peripheral portions subsequently come into contact with each otherand become frictionally melted. Thus, whole surefaces of the respectivejoining end portions 16, 17 of the core material 11 and the shaftmaterial 14 become melted. As just described, by the frictional heatingoccurring gradually from the central portions toward the peripheralportions and by the melted metal playing, so to speak, a lubricant-esquerole, a frictional torque between the core material 11 and the shaftmaterial 14 is kept small, and a motor having small power can be usedeven when the diameters of the joining end portions 16, 17 are large.

After frictionally heating and melting the joining end portions 16, 17of the core material 11 and the shaft material 14 as described above,the joining end portions 16, 17 of the core material 11 and the shaftmaterial 14 become joined (upset) by strongly pressing the core material11 to the shaft material 14 through the hydraulic cylinder 24 andstopping the rotation of the shaft material 14. More specifically, themetals melted by the frictional heating of the joining end portions 16,17 of the core material 11 and the shaft material 14 becomecooled/solidified (cooled and then solidified), and the core material 11and the shaft material 14 consequently become solidly joined.

Here, the strong pressing of the core material 11 to the shaft material14 after the frictional heating is not specifically limited as long asthe joint strength between the core material 11 and the shaft material14 can be heightened enough. However, the strong pressing force is morepowerful than the above pressing force at the time of the frictionalheating, and is, for example, about 20 MPa or more and 80 MPa or less(preferably, the lower limit is 30 MPa and the upper limit is 60 MPa).

Timing to stop the rotation of the shaft material 14 can be set by theamount of deformation caused by the softening (melting) of the joiningend portions 16, 17 of the core material 11 and the shaft material 14 atthe time of frictionally heating the joining end portions 16 and 17.However, the foregoing timing can also be set by the time having passedsince the starting timing of the strong pressing in which the corematerial 11 is strongly pressed to the shaft material 14 (e.g., 5seconds or less).

Lastly, descriptions will be given on the finishing process.

In the finishing process, finish processing is performed on africtionally joined mill roll. First, a frictionally joined mill roll isroughly processed to a state close to a finished state. Then, thermalrefining, i.e., heat treatment such as predetermined hardening andtempering, is performed. Next, by machining the thermally refined millroll in a product shape appropriate to the intended use, the mill roll10 is manufactured.

It is preferred to expose a metal surface by machining the interface ofthe roll barrel member 13 and the shaft material 14 after theearlier-described friction pressure welding process, and to performcircumferential welding (build-up welding) on the interface.

Additionally, as described above, it is preferred to perform anultrasound examination on the interface after exposing the metal surfaceof the interface of the roll barrel member 13 and the shaft material 14to examine whether the roll barrel member 13 and the shaft material 14are joined in good condition or not (quality inspection).

Next, with reference to FIGS. 1 and 5, descriptions will be given on amethod for manufacturing a mill roll according to the second embodimentof the present invention. This method is substantially the same as themethod for manufacturing a mill roll according to the first embodimentof the present invention described earlier except for the usage of themanufacturing apparatus of a mill roll 60, therefore, descriptions willbe given only on the different parts.

First, descriptions will be given on the preparatory process.

The roll barrel member 13 and the shaft materials 14, 15 prepared in themethod for manufacturing a mill roll according to the first embodimentof the present invention described earlier are carried to themanufacturing apparatus of a mill roll 60, the clamp 62 is made to holdthe roll barrel member 13, and the chuck 63 is made to hold the shaftmaterial 14 (the same applies to the shaft material 15).

Then, the relative position of the clamp 62 and the chuck 63 is adjustedin order to make the axial center of the core material 11 of the rollbarrel member 13 and the axial center of the shaft material 14 alignedwith each other.

Next, descriptions will be given on the preheating process.

In the preheating process, as shown in the method for manufacturing amill roll according to the first embodiment described earlier, by theearlier-described preheating means, the joining end portion 16 of theroll barrel member 13 and the joining end portion 17 of the shaftmaterial 14 (or the shaft material 15, the same applies hereafter) arepreheated to a pre-set temperature.

Next, descriptions will be given on the friction pressure weldingprocess.

First, under a condition where the axial center of the shaft material 14is aligned with the axial center of the core material 11 preheated inthe above preheating process, by rotating the chuck 63 (the shaftmaterials 14, 15) through a motor while pressing the shaft material 14to the core material 11 through a pressing means, the joining endportions 16, 17 of the core material 11 and the shaft material 14 becomefrictionally heated.

The pressing force of the core material 11 shown in the method formanufacturing a mill roll according to the first embodiment describedearlier can be applied as a pressing force of the shaft material 14.

As described above, after frictionally heating the joining end portions16, 17 of the core material 11 and the shaft material 14, the corematerial 11 and the shaft material 14 become joined by strongly pressingthe shaft material 14 to the core material 11 through the pressing meansand stopping the rotation of the shaft material 14. The strong pressingforce of the core material 11 shown in the method for manufacturing amill roll according to the first embodiment described earlier can beapplied as a strong pressing force of the shaft material 14.

Lastly, descriptions will be given on the finishing process.

By performing finish processing on a mill roll frictionally joined bythe method shown in the method for manufacturing a mill roll accordingto the first embodiment described earlier, the mill roll 10 ismanufactured. It is preferred to expose a metal surface by machining theinterface of the roll barrel member 13 and the shaft material 14 and toperform circumferential welding (build-up welding) on the interfaceafter the earlier-described friction pressure welding process. It isalso preferred to perform an ultrasound examination on the interfaceafter exposing the metal surface of the interface in order to examinewhether the roll barrel member 13 and the shaft material 14 are joinedin good condition or not (quality inspection).

Next, with reference to FIGS. 6(A) to 6(C) and 7, descriptions will begiven on a different example of the preheating means used in thepreheating process. This preheating means includes a robot arm (it ispreferred to use a 6-axis polyarticular robot) 65 and a burner 67, therobot arm 65 having a well-known structure, the burner 67 being attachedto the tip portion of an arm 66 of the robot arm 65. The robot arm 65includes an unillustrated control part, determines the direction andmovement locus of the burner 67 in accordance with a program input intothe control part, and is capable of arranging the burner 67 at arbitraryposition in arbitrary direction. The burner 67 has a water-coolingstructure, and is made not to be heated by the heat given off by theburner 67 itself. The arm 66 of the robot arm 65 can also bewater-cooled as needed.

Therefore, by operating the robot arm 65, the burner 67 is normallyarranged at the standby position, however, when preheating the joiningend portion 16 (the same applies to 18) of the roll barrel member 13 andthe joining end portion 17 (the same applies to 19) of the shaftmaterial 14 (the same applies to 15), an adequate interspace is providedin between the joining end portion 16 of the roll barrel member 13 andthe joining end portion 17 of the shaft material 14, and the burner 67is arranged at the middle position of this interspace. Then, bydelivering inflammable gas (e.g., LPG, LNG) and oxygen (or air) to theburner 67, the burner 67 becomes lit. The number 69 indicates a waterjacket.

Next, by operating the robot arm 65, the burner 67 is directed to thejoining end portion 16 in order for the flame of the burner 67 tospirally heat the joining end portion 16. After finishing heating thejoining end portion 16, the burner 67 is rotated by 180 degrees in orderto spirally heat the joining end portion 17.

As to the spiral motion of the burner 67, the burner 67 may spirallymove from A to B in FIG. 6(B) (i.e., from the outer circumference to thecenter side), and may also spirally move from B to A in FIG. 6(B).

Additionally, as illustrated in D to C or C to D in FIG. 6(C), it ispossible for the burner 67 to move on a circle having a differentdiameter.

Also, when using a single burner 67, it is necessary to change the flameblowing direction of the burner 67 from one joining end portion 16 tothe other joining end portion 17 in a short period of time. Thus, asillustrated in FIG. 7, by arranging first and second burners 71, 72composing a burner back to back (angles differing by 180 degrees) andmaking both the first and second burners 71, 72 give off flame, both ofthe joining end portions 16, 17 can also be simultaneously heated.

Here, when the diameters of the joining end portions 16 and 17 aredifferent, it is preferred to provide valves 73, 74 for both the firstand second burners 71, 72. In the case of partial non-use of the secondburner 72 with respect to the small-diameter joining end portion 17, byturning off the valve 74, the joining end portion 17 can be non-heated.These first and second burners 71, 72 are provided at the tip of an armof an unillustrated robot arm.

By using the methods for manufacturing a mill roll of the presentinvention described above, a mill roll can be manufactured in ashortened work period and at a low cost, and an ever-longer life of amill roll can be achieved.

The descriptions have been given on the present invention hereinbeforewith reference to the embodiments, however, the present invention is notlimited to the structures described in the above embodiments, andincludes other embodiments and variations conceivable within the scopeof matters in the claims. For example, the scope of right of the presentinvention includes cases where a method for manufacturing a mill roll, amill roll and a manufacturing apparatus of a mill roll of the presentinvention are composed of combinations of part or all of the respectiveearlier-described embodiments and variations.

INDUSTRIAL APPLICABILITY

In the method for manufacturing a mill roll, the mill roll and themanufacturing apparatus of a mill roll according to the presentinvention, since a roll barrel member and a shaft material are joined bya preheating process and a friction pressure welding process, materialcosts can be cut down, and a higher-precision mill roll can bemanufactured by a method that is easier than ever before.

REFERENCE SIGNS LIST

10: mill roll, 11: core material, 12: tinkering hardfacing layer, 13:roll barrel member, 14, 15: shaft material, 16, 17, 18, 19: joining endportion, 20: manufacturing apparatus of a mill roll, 21: base stand, 22:clamp, 23: chuck (second holding means), 24: hydraulic cylinder(pressing means), 25, 26: supporting stand, 27: steady rest means, 28:table, 29: first holding means, 30: connecting rod, 31: preheatingmeans, 32: burner, 33: water-cooling means, 34, 35: water-coolingjacket, 36: mounting stand, 37, 38: pipe arrangement, 39, 40:heat-resistant plate (heat-resistant member), 41: opening portion, 42:gas supply tube, 43, 44: gas supply chamber, 45: preheating position,46: non-preheating position, 47: moving means, 48: guide rail, 49:carrying stand, 50: gas supply hose, 51: carriage, 52: guide roller, 53:floor surface, 60: manufacturing apparatus of a mill roll, 61: basestand, 62: clamp (first holding means), 63: chuck (second holdingmeans), 65: robot arm, 66: arm, 67: burner, 69: water jacket, 71, 72:burner, 73, 74: valve

The invention claimed is:
 1. A method for manufacturing a mill roll,comprising: a roll barrel member having a hard hardfacing layer formedon an outer circumference of a columnar core material consisting ofchromium-molybdenum steel or carbon steel; and shaft materialsconsisting of chromium-molybdenum steel and being singly provided onboth sides in an axial direction of the core material, wherein diametersof joining end portions of the shaft materials are made smaller than adiameter of the core material, the method for manufacturing a mill rollfurther comprising: a preheating process for preheating either one orboth of at least joining end portions of the roll barrel member and thejoining end portions of the shaft materials to a pre-set temperature;and a friction pressure welding process for, with axial centers of theshaft materials aligned with an axial center of the core material,joining the core material and the shaft materials by strongly pressingthe shaft materials to the core material after fractionally heating thejoining end portions of the core material and the shaft materials byrotating the shaft materials while pressing the shaft materials to thecore material.
 2. The method for manufacturing a mill roll according toclaim 1, wherein a preheat temperature for the joining end portions inthe preheating process is 500° C. or higher and a melting point of theshaft materials or lower.
 3. The method for manufacturing a mill rollaccording to claim 2, wherein the diameters of the joining end portionsof the shaft materials are 86% or more and 96% or less of the diameterof the core material.
 4. The method for manufacturing a mill rollaccording to claim 2, wherein the core material projects from endportions of the roll barrel member.
 5. The method for manufacturing amill roll according to claim 1, wherein after the friction pressurewelding process, a metal surface is exposed by machining interfaces ofthe roll barrel member and the shaft materials, and circumferentialwelding is performed on the interfaces.
 6. The method for manufacturinga mill roll according to claim 1, wherein a used roll having the newhardfacing layer formed on the outer circumference of the roll barrelmember is used as the roll barrel member.
 7. The method formanufacturing a mill roll according to claim 6, wherein the hardfacinglayer on the outer circumference is partially or entirely removed fromthe used roll by machining after annealing.